1. Field of the Invention
The present invention relates to an optical sensor which detects position of an object according to an optical beam shielding action of the object and an optical apparatus using such an optical sensor.
2. Description of the Prior Art
Conventionally, as a method for inspecting irregularities in an object, there has been known an inspection method using an optical apparatus in which moire fringes are utilized.
In the optical apparatus utilizing moire fringes, while a moire grating is disposed with a predetermined distance from a test object and illuminated with a light beam, the moire grating and the test object are observed from a direction different from the direction of the incident light beam, thereby inspecting the irregularities of the object.
Such an optical apparatus utilizing moire fringes is provided with means for supporting and moving the test object which supports the test object while allowing the latter to move in a predetermined direction so as to make the test object sufficiently approach the moire grating, thereby forming clear moire fringes.
However, in the above-mentioned conventional optical apparatus, in cases where a surface for supporting the test object in the means for supporting and moving the test object has an inclination, when the test object approaches the moire grating, a part of the test object may abut to the moire grating before the test object is placed at a predetermined approaching position, thereby damaging the moire grating. Also, due to fluctuation in size of the test object and mishandling of the test object, for example, the test object may abut to the moire grating.
In view of these problems, an optical sensor may be used to detect abnormal approaching of the test object to the moire grating. However, a normal optical sensor may not attain a sufficient accuracy in detection since it can recognize an object only along a single line which connects a light source and a light-receiving device together.
Also, in order to improve the accuracy in detection, a plurality of optical sensors may be disposed in parallel so as to detect the above-mentioned abnormal approaching. However, in this case, the apparatus may need a complicated configuration with a higher cost.
These problems are common not only in the optical apparatus utilizing moire fringes but also in cases where abnormal approaching may occur as well as in various cases where it is necessary to detect position of an object.